Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque
H,W = map(int,input().split())
s = list(input() for i in range(H))
board = [[1]*(W+2) for i in range(H+2)]
white = 0
for i in range(H):
    for j in range(W):
        if s[i][j] == '.':
            white += 1
            board[i+1][j+1] = 0
queue = deque([[1,1]])
v = [[1,0],[-1,0],[0,-1],[0,1]]
while queue != deque([]):
    x,y = queue.popleft()

    for a,b in v:
        if board[x+a][y+b] == 0:
            board[x+a][y+b] = board[x][y]+1
            queue.append([x+a,y+b])

if board[H][W] != 0:
    print(white-board[H][W]-1)
else:
    print(-1)